<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
<input type="password">
<button>显示密码</button>
<script>
  let input = document.querySelector('input');
  let button = document.querySelector('button');
  button.onclick = function(){
    if(input.type == 'text'){
      input.type = 'password';
      button.innerHTML = '显示密码';
    }else if(input.type == 'password'){
      input.type = 'text';
      button.innerHTML = '隐藏密码';

    }
  }
</script>
</body>
</html>